Photo-electrical transmission apparatus



Nov. 8, 1 92 7.

1,4,042 P. L. CLARK v PHOTO ELECTRICAL TRANSMISSION APPARATUS Filed Dec. 22, 1925 2 Sheets-Sheet l FIG-I 36C HQ. 8 A INVENTOR 2. Sheets-Sheet 2 HQ. l4

FIGJE.

P. L. CLARK PHOTO ELECTRICAL TRANSMISSION APPARATUS Filed Dec. 22, 1925 llllllll mils iii?

NQV. 19:27.

HE IS INVENTOR M Patented Nov. 8,1927

UNITED STATES PAUL L. CLARK, OF BROOKLYN, NEW YORK.

PHOTO-ELECTRICAL TRANSMISSION APBARATUS.

Application filed December 22, 1925. Serial No. 77,020.

My invention relates to improvements in apparatus for the transmission and receiving of electrical or 'electro-magnetic impulses either by wire or radio of point by point, line by line, scenes at one location so that an image of the said scenes may be produced simultaneously and registering accurately with the point by point light values of the original scene, as understood in the to art; and the object of the present invention is to provide a simple and efficient optical, electrical and mechanical arrangement applicable toboth the receiver and transmitter. Additional objects are pointed out .in the 36 following specification and claims, and

shown in the drawings. I

I attain these several objects by the mechanism illustrated in the accompanying drawings, in whichmechanism used for both or either the receiver or transmitter; Fig. 2 is a front elevation of Fig. 1, with parts broken away for clearness; Fig. 3 is a section of Fig. 2 on 3-3; Fig. 43 shows a part of a typical fila ment of a light source used in Fig. 8; Fig. 5 shows a speed varying or position changing element; Fig. 6 shows a typical light source;

Fig; 7 shows a grid such as used conjunctively in Fig, 8 Fig. 8 is a plan View of part of an optical system for the receiver, or with slight modifications. for the transmitter; Fig. 9-is a section of Fig. 8 on 9-9; Figs.

10 and 11 are enlarged views of-details of the optical systemyFig. 12 is a plan and Fig. 13 is an elevation of a speed changer or regulator; Fig, 14 is a diagram of connections for regulating the speed of the driving motor for the apparatus shown in Figs. 1, 2, 3; and Fig. 15 is a series of diagrams which show the individual effect on the optical system caused by the rotation or oscillation of the several cooperating or correlated elements of the apparatus. Fig. 16 is a detail of a modified receiver optical system; Fig. 17 isza detail of beam and lens intersection. I I

Similar numerals refer to similar parts in the several views, unless'otherwise noted.

y In Figs. '1, 2 and 3, a motor 1 drives a shaft 2 connected to a speed regulator 4 (see Figs. 5, 12'and 13) connected to the long coaxial shaft 5 turning in bearings ,11 and driving the gear 7, worm l2 and lens carrying wheel 25. Gear 7 meshes with gear 8 connected to shaft 10 infbearings 16 and Figure 1 is a plan View of part of the drives the polygonal mirror group 27 which revolves in a horizontal plane substantially bisected by the axis of the upper lens 26 in the wheel 25. Meshing with the worm 12 -is agear 13 on a shaft 14 which runs in bearing 16 and ends in the speed regulator.

mirror (this mirror may be concave or convex if desired, to vary the characteristics of the optical train) symmetrically disposed in front of the upper lens 26 in its central position. The function of this mechanism is to secure a relative location, rotation and oscillation of the several cooperating optical and mechanical elements to the end that a pencil of rays of controlled intensity passing through the lens 30 be intercepted by the shutter 19, focused substantially upon the periphery of'the mirror disk 27, reflected therefrom to register substantially upon and follow the approximate path of travel of the upper lens 26 during its transit across a given arc-(approximately equal'to chord 6, Fig. 8), said lens being of such focal length as to converge the rays to a focus at a given distance therefrom (which, in Fig. 2 is, after reflection by the mirror 24, at approximately the focal plane 40). The ratios and angular position of the gears, cam and other factors is such that the opaque portion of the shutter 19 cuts off the light beam 36* during the return motion of the cam 18; the angular velocity of the disk 25 and the are traversed by each lens 26 is such as to cause each .of said lenses when passing the field in front of the mirror 24 to successively intercept the unidirectional intermittently reflected beam 36 from each of the mirrors 28 of the group 27- during the rotation of said group and the simultaneous rotation of-said disk 25, the planes of rotation of said disk and said group being preferably at right angles, and the are (7, Fig. 8) subtended and traversed by each mirror in a given interval being proportional to that subtended by each lens 26 in the same interval the duration of which is the time required to register all component light point values comprising one transverse line or are of the transmitted picture. The gear ratios and 18 and shutter 19 are such that the mirror successive mirrors 28 of the group 27, which cooperate, follow and register each successively with oneof the lenses 26 during its passage across an arcuate area upon which are substantially superimposed in rapid succession beams of variable intensity proportional to the true light values of each picture point or area for projection to its correct registering position on the focal surface 40) are spaced or their edges juxtaposed or slightly overlapped by the tipping of the mirror 24 to'cause thebeam of light reflected 'by it to focus upon and entirely embrace, in its arc of reciprocation. the height of the desired view u on the surface 40, the arc of oscillation of t e mirror 24 during the interval required for the passage of a single lens 26 across the field of View, being very smallv as compared to the arc traversed by said lens; so-that as many lenses pass the field of view during the registering of one complete image as there are transverse lines comprising the whole picture; and the cam 1.8 makes only three-fourths (provided a three-to-one ratio cam is used) revolution during which the mirror 24 is optically operative in conjunction with the shutter 19, the remaining one-fourth revolution of thecam'being required to return the mirror to its starting position for the beginning of another cycle. The lens carrier wheel 25 continues to revolve at uniform speed, but no light passes to the lenses, as the shutter is so geared and timed as to intercept'the light rays during the return stroke. of the mirror to its starting position. Transverse deflection, positioning and timing of the picture points is accomplished by the uniformly spaced. identically mounted, accurately matched lenses moving at uniform velocity and supported by the disk 25 equally distant fromits cen-' ter of rotation, so that each lens functions successively in identical manner, in coopera-- tion with'the mirrors comprising group 27. each of which traverses a line or arc; and

vertical deflection, positioning and timing of these lines is secured by the mirror 24 which moves at, preferably a uniform rate of speed and the amplitude of which is controlled by the design of the cam 18 and connecting arm 21. The above-described optical and -mechanical system applies particularly to thedevice when used as a receiver; but by considering the direction of the light rays f neeama reversed- (to that shown by the arrowed lines on the light beams) the agparatus becomes a transmitting instrument 1 a photo-electric cell be placed at the focus of or in the path of the rays passing in reverse direction to or through the lens 30, Figs. 1 and 8, provided said cell be connected through a suitable circuit, as understood in the art. The mirror group may be made of reflecting metal, each mirror.being identical, all mirrors contacting on their edges, and each subtending an equal angle with respect to the axis of rotation of the group. The devices 4 (see Figs, 5 and 12.) are used for independently bringing into synchronism and step the mechanlsm either as a whole or "each element separately, devices for the same purpose having been. shown in British Patent 218,766. All spindles should be provided with collars (not shown) to prevent end play, and set screws to secure the several parts in proper alinement, and the optical parts enclosed in a light-tight housing, as is customary. The transmitter need not necessarily be of the same type as the receiver, provided the correct picture proportions. are maintained. Means for deflecting the light beam to approximately traverse and follow lenses or apertures in a rotatable disk are described in my copending application Ser. No, 655,027, which also shows several types of lens mountings applicable to the lens wheel 25.

In Fig. 4 the diameter a of the filament '35 should be preferably less than one-half of the spacing h and width at of the grids as shown in Figs. 7 and 8. The length of the filament may be as desired; but ordinarily should be about twice its diameter.

In Fig. 5, the driving shaft 2 and driven shaft 5 are attached to gears 48. 47, and turn in bearings in the frame 51. Gears 49, 50, turn on shafts integralwith the frame 51. By turning the handle 52 about the axis of the shafts 2, 5, angular displacement between the shafts 5 and 2 is attained In Fig. 6, the incandescent lam filament 35 is of small diameter, and when t is source is used in connection with the optical system of Figs. 8, 9, 10-and 11, the mirrors 32. Fig. 8; 32, Fig. 11, may be of any desired length to embrace the light rays from the re quired length of filament; although in Figs. 8 and 9 the width of the beam at its plane of interception by the mirror 32 should be very small, this restriction does not apply to the system shown in Fig. 11.

In Fig. 7, the grid 31 of opaque material has apertures 54 and opaque strips 55 pre-- meet optical requirements, depending upon the spacing, characteristics, focal lengths and design of the several lenses, mirrors and grids distributed for most useful and efiicient service on the optical axis. Similar grids are shown in ,mycopending application, Ser. No. 715,350.

In'Figs. 8 and 9, rays 36 from the source 35 are received upon and refracted by the accurately ground lens 34. Some of the rays are intercepted by the grid 31 and some rays pass through to focus upon or near the mirror 32 which is an ocillograph minror or other light deflecting device responsive to photoelectric signals emanating from a sending station, as described in my copending applications Ser. Nos, 715,350 and 13,- 306, the deflection of this mirror for maximum signal strength being sufficient to cause the light and dark strips comprising the image of grid 31 to fall upon, register with, and to be superimposed over respectively the. apertures and bars of grid 31; and for zero deflection to cause the light transmitting areas of the image of rid, 31 to register upon and be intercepted y the opaque parts of the grid 31, so that pract-ically no light from the source 35 reaches the lens'30. In case inverse values of picture point light values is transmitted by the sending station. the relative action of the grids images should be reversed from that stated above, so that a maximum received impluse would cause a superimposition of the dark image of grid 31 to be superimposed over the grid 31. The grids are preferably disposed adjacent the lenses as shown, and between the mirror 32 and the lenses, although they may be for equally good results placed either side of the lenses. For best, results the lenses and all parts of the mechanism should be made with extreme accuracy and precision. The optical system, as thus far described, comprises a light valve controlling the strength, proportional to photo-electric impulses, of the pencil of rays received upon the mirror 28 of the group '27. The relation between the distance g7v (between the central plane of the lens wheel 25 andthe point of reflection of the rays from themirror 28), the chord 6 (across thearc of travel of the optical axis of the lens during itsfunctioning period), and the angle f (subtended by each mirror 28), should be approximately such that The mirror group 27 should ordinarly comprise thirty or more mirrors, and the disk 25 should have eight or more lenses of identical characteristics and satisfying the optical conditions shown in the drawings. 4 When used as a transmitter. the grids and mirror 32 should be omitted and a photo-electric cell substituted for the mirror. In Fig.9,

. .f= ten" are shown three positions of the pencils 37 38, 39, focused upon the surface 40, which ordinarily is not a true plane, as pointed out in the description of Fig. 15, and if a screen be placed here the image may be viewed directly; if, however, it is desired to project the aerial image formed at 40 to a larger screen, an objective lens 46 should be used disposed n the optical axis and focused upon the surjface 40 and the said screen (not shown).

In Fig. 10, the incident pencil of rays is focused upon a circle 44 circumscribed around the polygon formed by the contacting mirrors 28, as shown by the arrowed lines.

In Fig-1 1, an oscillograph mirror 32 is shown completely embraced in three typical pencils of rays56, 57, 58, from a source of greater diameter than shown in Fig. 8: Since it is practically impossible to secure a point source of light of sufficient intensity for practical projection, it is essential that either the source or the mirror be of dimensions determined by the size of the points of light'at their intersection with the screen or the focal plane 40, Fig. 9; since if the point of light [which is in reality (for best,

importance, since it-together' with other o tical factorsdetermines the practicability of the apparatus. In other words, there must be somewhere in the optical train a means for limiting the picture point size, and this is accomplished by applicanteither by the use of a small light source, as in Fig. 8, or bv a small diameter oscillograph mirror, as in Fig. 11; or both. It is evident that the lenses, light source, grids, shutters, oscillograph mirror, mirrorwheel and oscillating mirror are to be suitably alined on a given optical axis, or on a plurality of intersecting optical axes. as understood in the art, and that the light beam should be approximately symmetrical with respect to said axis, or the plane of said axis.

In Figs. 12 and 13, gears 67 and 69 are free toturn on the coaxial shafts 72, 72, held by the frame 7 3, Gears 66. 68 are attached to coaxial shafts 2. 5, which turn in the frame 73 and are at right angles to'shafts 72. and are the driving and driven shafts. as shownin Figs, 1 and 2. Lugs 71 are attached. to shafts- 72, and, to these lugs is rigidly attached the arms 112 of the metal. member 75 having a hub 76, so that the entire mechanism is free to revolve on shafts 2 and the motor 1, Fig. 1), supplied from a suitable 5 as an axis. The handle 85 has a bearing 88 on shaft 2, which bearing extends upwardly to form a sleeve 87 on which is secured a flanged insulator 89 which securel holds a contacting arm 90 hearing on a coi ed resistance wire 92 grounded to the member 75 by a screw 95; so that if the handle 85 be turned about shaft 2, the contact travels over different turns of the coil 92 and thereby varies the length of resistance wire between the point of contact and the ground connection. Lu s 86 on the handle 85 bear against flexible springs 79 rigidly held in the members 81, 81 pivoted on studs 82 attached to the member 75 and adjustable by means of screws 84 in lugs 83, and screws 78 in lugs 77 integral with the member 75. The adjustment of screws 78 should be such as to aline the springs for zero pressure against and in contact with the lugs 86 when the handle 85 iin approximately central position, as shown. The adjustment of screws 84 should be such as to produce a force in the springs 79, 79 at their points of contact with lugs 86, equal to the counter force required at the said points of contact to overcome the friction produced by changing the angular position of the parts rotatable about the shafts 2, 5,.including sliding friction of the contact arm over the resistance 92, when the apparatus is running at normal synchronous speed. The relation between the strength and elasticity of the springs 7 9, in comparison to the resistance of the coil out out of.or

added to the circuit, should be such that any change in the: an ular velocity or speed of (i. e., overcomin' inertia or adding or reducing momentum rotating or oscillating masses produced by the turning of the member and its correlated parts through any given angle will add to or subtract from the normal driving power of the prime mover at synchronous speed, in such manner as to automatically provide an instantaneous variable power increment to the motor independent of the normal synchronous speed power requirements, the amount of added or decreased power being substantially proportional to the deflection roduced in either one of the springs 79, handle 85. If the motor" is assisted by turning the handle 85, less power will be required; if the motor. is retarded, more power will be required to supply the force equal to and counterto the retardin force, in order to maintain. synchronous spee under constant load. The-control of power to the motor may be accomplished in any well known manner, and I have here shown the regulation as being madeby the introduction of the variable resistance 92 in series with the field circuit 90, 9.6, 97, 9s, 99, 102,101, metal member 75, 95, of a constant -speed shunt wound motor 100, (corresponding to 9, by turning the.

source 102. When more than one regulating or compensating device is used,"as is necessary in Fig. 1, the regulating circuits on all the regulators may be connected in series or multiple, in order to deliver at the normally excited motor field a net current change equal to the algebraic sum ofthe several instantaneous currentchanges (whether positive or negative, depending upon whether the motor is retarded oraccelerated by the manual turning of the handle when one or more of said regulating devices be adjusted-separately or simultaneously. These changes in motive power should ordinarily be proportional to and simultaneous with the deflection produced in one or more of the tension'springs 79, 79, by applying the or moved, the power to overcome inertia being supplied by the motor whose field is weakened or strengthened proportionally to the deflection produced in the springs 7 9, 79 when the position of the gears and parts connected to -them is rotated b turning the said handle, which turning 1s for the purpose of phasing either the picture line or point positions on the screen to register with the picture sent or broadcasted by the transmitting station apparatus. This device is applicable to any type of mechanism requiring delicate speed adjustments, or changes in phasing, speed or position of any moving parts with relation to the position or speed of any type of driving mechanism connected to drive said moving parts. It is known that varying the field strength of a vshunt wound motor varies its' speed; or, considering the speed as constant, varying the field will automatically produce an inverse variation in armature current to provide changes in power as required.

In Fig. 14, a battery 103 is connected across the terminals of an adjustable resistance 104 having a slider 105 making contact therewith; the combination of this resistance and slider being analagous to that of coil 92 and slider 90, Fig. 12. The slider is connected to the grid of an audion the plate of which is connected to a solenoid 108. so that as the grid current varies, the plate current is amplified to move an arm 109 attached to the solenoid plunger andyary the characteristics of a field rheostat or other regulating means 110. suitably-cooperating with a driving device (not sh0wn).-

In Fig. 15, E is the position of the plane of deflection of rays from the edge, and M the plane of deflection from the middle of one of the mirrors on the disk 27, the action ofthis disk in revolving being to produce an out-of-focus effect on a plane surface, so that the optical plane for the rays from the edges of the mirror. is beyond the optical plane for the rays from its middle or intermedlate points; so that since this disk 27 revolves in a horizontal plane, the distortion" tion which would be produced by the lenses 26 if the rays were directed to fall upon them in a true plane is neutralized by the rays actually striking them in beams of a length which is greater for the said lenses in their outside than in their intermediate positions, so that the resultant ofthe two curved focal surfaces H and H is to produce a substantially true and uniform focal distance for the rays which pass through the lenses 26. E is the position of the plane of refraction of the lenses 26 at the side or edge of their operative arc of travel, and M is their position at the middle of said arc, P and Q being their respective foci. The effect of the oscillating mirror 24 is to require for both horizontall and vertically reflected rays a concave 'ocal surface, as shown at V and H The best resultant focal surface being therefore approximately a concave surface, as determined principally by the combination of the curves V and H; and the lenses 46, Fig. 9, should be selected with this in View.

A light source of any suitable area and dimensions may be used with the apparatus and the rid widths and spacing varied to meet di erent optical conditions due to spreading of the light beam on account of its size. The lenses in the light beam should I be of different diameters and characteristics as required; and for the arrangement in Fig. 8, the lens 30 should be about three times the diameter of the lens 34; and the 'd 31 should be designed with respect to t e grid 31 but of about three times its dimensions, provided the light source be of a diameter equal h, Fig. 7. 'The spacing of the grids is best determined graphically, it being understood that their function is to provide a light valve in conjunction with the mirror 32, so that when said mirror is at zero deflection no light will pass through the second grid as the bars of the'second id shut ofi' all light which passes through t e apertures .of the first grid; and when mirror 32 isat maximum deflection all the vertical light bars which pass through the first grid should exactly register over and pass through the apertures on the second grid; intermediate light values are proportional to the mirror deflection with consequent overlap ing of the light beams over part of the grid ars ,ofthe second grid. The maximum mirror deflection should ordinarily be such as to cause the vertical bars of light to travel horizontally a distance equal to the grid spacing of the second grid. The bars of the grids should ordinarily be parallel to the axis of oscillation of the mirror 32 (or other deflecting device, such as a cathode ray oscillograph) and to the lamp filament.

An oblique mirror positioned in front of a rotating explorer or disk is shown in Fig. 1, of my copending application Ser. No. 715,- 350. The regulator of Figs. 12 and 14 may be advantageously used between any source of applied energy and a part or parts whose angular or linear position is to be changed relative to the speed or direction of the said source of energy.

In Fig. 16, light rays from a source 35 pass through and are filtered by the grid 31*, the rays which pass through entering the lens 120 which produces an image of the source on the plane 125 where the rays cross the axis 126; these rays enter the lense 121' and are focused to produce an image of the source at or near the mirror 32 which reflects the rays to a lens 122 which focuses the rays upon the mirror wheel 27 which reflects the 'rays as shown and as in Figs. 8 and 9. The grid 31 is placed near lens 122. The grids should be designed so that the rays which pass through the apertures in grid 31 will also pass through the apertures in grid 31 for a predetermined position or deflection of the mirror 32, generally for a maximum deflection of the mirror. A somewhat similar arrangement is shown in Fig. 28 of my application Ser. No. 715,350; and the grids may be of thin metal between glass plates, as shown in Fig. 27 of the same application.

In Fig. 17, the area 123 indicates the area approximately covered successively by each of the lenses 26, Figs. 1, 2, etc., at the plane of the wheel 25, said area being for best efiiciency and evenness of illumination, sufiicient to include the area 124 which indicates the intersection of the light beam from each successive plane mirror of the mirror wheel register substantially with said lenses and follow their approximate path of travel across a given arcuate area.

It is feasible to employ any other type of light valve than thatshown in Figs. 8 and 16; but I prefer to'employ the mirror wheel 27' in combination with the lens wheel 25 and the oscillating mirror 24 all functioning and coacting to distribute the received picture point lighting values and distributing the pencils of rays reflected and refracted by them so as to register at approximately their correct positions'on the receiving screen in order to faithfully reproduce at the distant station an image of the scene as sent from a distant station. It is obviousthat the lenses is decreased, and means for restoring normal may be replaced by concave focusing reflec-' driving. ower to the tors (not shown) or other light'condensing speed or the said'optical means relative to in passing across the field of view requires an equal period of time when the apparatus these lenses be considered as relatively small tially synchronous speed tical means and simultaneously. varying the varying the speed of said optical means and cally connecte the motor-if the speed of e optical means said beamsactually instantaneously to said first optical means, means for promaintaining driving means. The size of each lens 26'is relatively the motor speed reaches a fixed value. small with respect to the field of view as pro- 4. In apparatus for the transmission of jected to a projection screen,.and each lens visual images, in combination, movable optical means, a suitable motor for driving said means normally at a given synchronous is running at uniform speed. Each lens 26 speed, and means for momentarily producing is mounted inan aperture of the wheel 25, asynchronous speed of the optical means said wheel being of opaque material, and if and simultaneously maintainmg substan- 1%)011 said motor i. e., if each by the application thereto 0 variable power. lens intercepts but a narrow. cone of rays, 5. In apparatus for the transmission of then the View as projected in successive lines visual images, in combination, a motor, movupon the wheel may be considered as beable optical means coupled to-saidmotor and ing an out-of-t'ocus view, since each succesdisposed to be driven thereby, a controller sive light beam overlaps the next light beam, for varying the relative speeds of said motor comprisand sa1d optical 'means, said controller ining the rays to produce the true light values cluding means connected to said motor for of adjacent picture points. The mirror 32 varying the torque between said motor and or- 32 may be -concave or convex, if desired. said optical means proportional to the m The use of a concavemirror is shown in my nitude of variation of said relative spee s. copending application Ser. No. 162,311, 6. In apparatus for the transmission of claim visual images, in combination, movable op- 1. In apparatus for the transmission of 'tical means, a motor for normally. driving with respect to the field of view,

tical means when thevisual images in combination, movable opsaid means at a speed profportional tothetical-means, an electric motor for driving motor speed, and means said means in synchronism with ,a second varying the speed of said optical means relaoptical means, saidmotor being connected tive tothe motorspeed and simultaneously substantially synchronous moducing asynchronous speed of the first optor speed. 4

power of the motor. visual images, in combination, movable op- 2. In apparatus for the transmission of tical means a motor, a phase changer, and visual images, in combination, movable opan electrical connection between said phase tical'means, suitable driving means connectchanger and said motor, said motor, hase ed to said optical means, and means for changer and taptical means being mec anisimultaneously varying the torque of said 8. In apparatus for the;transmission of means. w visual images, in combination, movable op- 3. In apparatus forthe transmission of ticalmeans a motor, a phase changer, and visual images, in combination, movable opan electrical current control device, said contical m'e'ans, anelectric motor, the armature trol device,-being actuated by-the movement ofsaid motor being connected to drive said ofsaid hase changer, and an electrical conoptical means, means for varying the absolute nection tween said control device and said speed of said optical means; means for inmotor. f creasing the power applied to the motor if In testimony whereof, I, Paul L. Clark, the speed ofpthe optical means is-incr'eased, have signed my'name' tothis specification, means for decreasing the wer applied to this 21st day 'of December, 1925. PAUL L. CLARK.

7. In apparatus for the'transmission of or momentarily 

